System and method for receiving and transmitting information in a multipath environment

ABSTRACT

A system and a method for receiving and transmitting information in a multipath environment provide a wireless communications system. The wireless communications system provides a switching module that is adapted to couple a receiver module to either a first antenna or a second antenna as a function of reception characteristics of the first antenna and the second antenna. The switching module is also adapted to couple a transmitter module to the either the first antenna or the second antenna as a function of transmission characteristics of the first antenna and the second antenna.

RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 09/902,035, filedJul. 10, 2001, which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention generally relates to a system and a method forreceiving and transmitting information using wireless networks and, morespecifically, to an antenna system and a method for receiving andtransmitting information in a wireless multipath environment.

BACKGROUND

A signal that is received or transmitted by a conventional wirelesscommunications device in a wireless communications network is influencedby the surrounding environment. In theory, a conventional wirelesscommunications device that has a single antenna 200 would have aradiation pattern as shown in a polar plot illustrated in FIG. 3. Thesingle antenna 200 has an isotropic radiation pattern 210 illustratedwith an isotropic gain line 220 of, for example, 0 dBi. Althoughradiation patterns are three dimensional, it is understood that thepolar plots are merely two-dimensional representations. Thus, a polarplot may represent, for example, a cross section of a three-dimensionalradiation pattern. In addition, the phrase “radiation pattern” is to bedefined as including at least transmission patterns or receptionpatterns. The isotropic radiation pattern 210 is a theoretical, idealmodel occurring, for example, in the remote vacuum of space with a pointsource of radiation.

In practical settings, for example, in an urban environment, multipathand other considerations create nonuniformities in the radiationpatterns. A signal may bounce off, for example, the ground, buildings,walls or other reflecting structures before reaching the single antenna200 of the conventional wireless communications device. Furthermore,since a signal may be scattered simultaneously across a plurality ofpaths in space and time before reaching the single antenna, the signalmay interfere constructively and destructively with itself. FIG. 4 showsanother polar plot illustrating an example of a multipath radiationpattern 260 including a gain line 230 generated from the single antenna200. The gain line 230 has been distorted due to multipath interference.Thus, for example, points 240, 250, although equidistant from the singleantenna, effectively see different radiation patterns in which the point240 sees greater signal gain than the point 250.

Therefore, a user of the conventional wireless communications device,that is suffering from poor reception or transmission due to multipathconditions, typically may need to physically move around in a randomsearch for an improved signal (e.g., move from the point 250 to thepoint 240 without knowledge of the shape of the radiation pattern 260).Such physical translations of the conventional wireless communicationsdevice are not convenient and may not even be available under certainconditions such as, for example, when the user may not be free to movearound.

In addition, since multipath effects result, in part, from constructiveand destructive interference of signals, multipath effects differ atdifferent signal frequencies. Thus, for example, as shown in a polarplot illustrated in FIG. 5, a first gain line 270 is generated by thesingle antenna 200 at a first frequency f₁ and a second gain line 280 isgenerated by the single antenna 200 at a second frequency f₂.

The conventional wireless communications device may transmit and receivesignals at different frequencies. Thus, for example, via the singleantenna, the conventional wireless communications device may transmit atthe first frequency f₁ and receive at the second frequency f₂. Theconventional wireless communications device effectively experiences, forexample, a radiation pattern for transmission as represented by the gainline 270 and a radiation pattern for reception as represented by thegain line 280. The consequences during, for example, two-way wirelesscommunications between the single antenna 200 and a point 290 (e.g., abase station) are further illustrated in FIG. 5. The point 290 and theantenna 200 effectively experience disparate radiation patternsdepending upon whether the single antenna 200 is transmitting orreceiving. In this case, the single antenna 200 effectively experiencessubstantially more gain in receiving signals from the point 290 than intransmitting signals to the point 290. Thus, it is possible, forexample, that although the signal from the point 290 is successfullyreceived, the signal transmitted to the point 290 may be lost.

SUMMARY

In one embodiment, the present invention provides a system and a methodfor receiving and transmitting information in a multipath environmentincluding a first antenna, a second antenna, a switching module, areceiver module and a transmitter module. The switching module isadapted to couple the receiver module to one of the first antenna or thesecond antenna as a function of reception characteristics of the firstantenna and the second antenna. The switching module is also adapted tocouple the transmitter module to one of the first antenna or the secondantenna as a function of transmission characteristics of the firstantenna and the second antenna.

The present invention has an advantage in that the wirelesscommunications device provides the first antenna and the second antennafrom which the wireless communications device can select to optimizetransmission characteristics or reception characteristics. The presentinvention has an advantage in that the wireless communications devicecan automatically couple the transmitting module to the antenna thatprovides the best transmission characteristics. The present inventionalso has an advantage in that the wireless communications device canautomatically couple the receiving module to the antenna that providesthe best reception characteristics.

These and other features and advantages of the present invention will beappreciated from review of the following detailed description of thepresent invention, along with the accompanying figures in which likereference numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of some components of a wirelesscommunications device according to the present invention.

FIG. 2A is an illustration of a wireless device according to the presentinvention.

FIG. 2B is an illustration of a wireless device according to the presentinvention.

FIG. 3 shows a polar plot of an isotropic radiation pattern for aconventional antenna.

FIG. 4 shows a polar plot of a radiation pattern in a multipathenvironment for a conventional antenna.

FIG. 5 shows a polar plot of a radiation pattern at differentfrequencies in a multipath environment for a conventional antenna.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary embodiment of a wireless communicationssystem including a wireless communications device 100 according to thepresent invention. The wireless communications device 100 may include,for example, a handheld wireless communications device, a mobile phone,a car phone, a cellular or a personal communications services (PCS)phone, a cordless phone, a laptop computer or other computing devicewith a wireless modem, a pager or a personal digital assistant (PDA).The wireless device 100 may be digital or analog or some combinationthereof. Indeed, the present invention also contemplates other forms ofwireless communications devices known to one of ordinary skill in theart.

The wireless communications device 100 may include, for example, a firstantenna 110, a second antenna 120, a switching module 130, a transmittermodule 140, a receiver module 150 and a main controller 160. Theswitching module 130 may include, for example, a receiver switch 170 anda transmitter switch 180. The main controller 160 may include, forexample, a mobile station modem (MSM) or other processor that isprogrammable. The wireless communications device 100 may also includeother components (e.g., duplexers, diplexers, amplifiers, mixers,filters, oscillators, etc.) which are known to one of ordinary skill inthe art and not shown or described further herein.

Referring now to FIGS. 2A and 2B, the wireless communications device 100is shown in one possible arrangement. In this example, the wirelesscommunications device 100 includes two antennas: the first antenna 110in a first orientation, and the second antenna 120 oriented in a secondorientation. Preferably, the first antenna 110 will be positioned in anorthogonal relationship or in another relationship that accentuatesdiffering gain patterns from the first antenna 110 and the secondantenna 120. Also, in this example, the first antenna 110 is mountedsuch that the antenna extends, at least in part, outside the housing ofthe wireless communications device 100, while the second antenna 120 ismounted inside the housing. It will be appreciated that other antennamounting orientations and locations may be selected to support specificapplications and aesthetic considerations.

In the illustrated example, the wireless communications device 100transmits at frequency f₁ as shown in FIG. 2A and receives at frequencyf₂ as shown in FIG. 2B. As previously described, it is likely that eachantenna 110, 120 will have a different gain line at the frequency f₁ ascompared to the gain line at the frequency f₂. For example, the firstantenna 110 has a radiation pattern with a gain line 115 when operatingat the frequency f₁ as illustrated in FIG. 2A and a radiation patternwith a gain line 116 when operating at frequency f₂ as illustrated inFIG. 2B. In a similar manner, the second antenna 120 has a radiationpattern with a gain line 125 when operating at frequency f₁ asillustrated in FIG. 2A and a radiation pattern with a gain line 126 whenoperating at frequency f₂ as illustrated in FIG. 2B.

The wireless communications device 100 advantageously uses thedifference in gain lines, such as, for example, between the gain line115 and the gain line 125 or between the gain line 116 and the gain line126, to enhance operation of the wireless communications device 100. Forexample, the wireless communications device 100 may determine which ofthe first antenna 110 or the second antenna 120 is better fortransmitting or receiving a communications signal and may select thebetter antenna for current communications. In such a manner, moreconsistent signal quality may be obtained, which may, for example,reduce dropped calls, enable lower power usage, or permit faster datatransmissions. Since gain lines may vary in response, for example, tomovements of the wireless communications device 100 or to changes in theenvironment, the wireless communications device 100 may continuallydetermine and select the better antenna. Accordingly, the wirelesscommunications device 100 may maintain a more consistent signal qualityeven when moving or when operated in an active, dynamic environment.

Referring again to FIG. 1, the wireless communications device 100 isdescribed in more detail. The main controller 160 is coupled to thetransmitter module 140, the receiver module 150 and the switching module130. The transmitter module 140 is coupled to the transmitter switch 180of the switching module 130. Via the transmitter switch 180, thetransmitter module 140 can be coupled to one of the first antenna 110 orthe second antenna 120. The receiver module 150 is coupled to thereceiver switch 170 of the switching module 130. Via the receiver switch170, the receiver module 160 can be coupled to one of the first antenna110 or the second antenna 120.

Although illustrated as being in generally in the same direction, thefirst antenna 110 and the second antenna 120 can be disposed at an angleto each other. For example, the first antenna 110 is preferably disposedin a direction that is approximately orthogonal to the second antenna120. Since the orientation of an antenna affects its radiation pattern,the first antenna 110 and the second antenna 120 may have differentradiation patterns. Thus, the second antenna 120 may provide analternative radiation pattern for the wireless communications device100.

In operation according to an exemplary embodiment, the main controller160 receives a signal from a base station of a wireless communicationsnetwork via the first antenna 110 or the second antenna 120. Based onthe signal, the main controller 160 sets the transmitting module 140 totransmit, for example, at a frequency f₁ and the receiving module 150 toreceive at a frequency f₂. The main controller 160 can evaluate whichantenna 110, 120 provides the best reception characteristics at thefrequency f₂ in the present environment, which may include multiplepaths. The main controller 160 can also evaluate which antenna 110, 120provides the best transmission characteristics (e.g., signal strength,clarity, bit error rate, etc.) at the frequency f₁ in the presentenvironment. The evaluations can take place periodically oraperiodically (e.g., triggered by a particular condition). Based on theevaluations, the main controller 160 can control the switching module130 to switch the transmitter module 140 or the receiver module 150 tothe appropriate antenna 110, 120.

For example, during two-way communications between the wirelesscommunications device 100 and a base station in a wirelesscommunications network (e.g., a two-way conversation between connectedcallers), the main controller 160 may determine, for example, that forthe assigned channel at frequency f₂, the first antenna 110 providessuperior reception to the second antenna 120 in the present environment.Thus, the main controller 160 sends a control signal to the switchingmodule 130 that causes the first switch 170 to couple the receivermodule 150 to the first antenna 110. The main controller 160 may alsodetermine, for example, that for the assigned channel at frequency f₁,the first antenna 110 provides superior transmission in the presentenvironment. Thus, the main controller 160 sends a control signal to theswitching module 130 that causes the second switch 180 to couple thetransmitter module 140 to the first antenna 110.

In operation according to another exemplary embodiment, the receivermodule 150 is coupled to, for example, the first antenna 110 via thefirst switch 170 of the switching module 130. The main controller 160monitors the reception characteristics of the first antenna 110. If thereception characteristics become poor (e.g., the bit error rate exceedsor is nearing an applicable error threshold), then the main controller160 tests the reception characteristics of the second antenna 110. Forexample, the main controller 160 may control the switching module 130such that the first switch 170 couples the receiver module 150 to thesecond antenna 120 in order to evaluate the reception characteristics ofthe second antenna 120. This can be accomplished relatively quickly. Forexample, if the reception characteristic of the second antenna 120 isevaluated based on, for example, the error bit rate of the secondantenna 120, then an evaluation can be determined even on a bit-by-bitbasis.

If the main controller 160 determines that the second antenna 120 hasbetter reception characteristics (e.g., a lower bit error rate), thenthe main controller 160 may keep the receiver module 150 coupled to thesecond antenna 120. The main controller 160 then monitors the receptioncharacteristics of the second antenna 120. On the other hand, if themain controller 160 determines that the second antenna 120 does not havethe better reception characteristics, then the main controller 160 maycontrol the switching module such that the first switch maintains thecoupling between the receiver module 150 and the first antenna 110.

A similar procedure may be implemented by the main controller 160 inmonitoring the transmission characteristics of the antennas 110, 120.For example, the main controller 160 may monitor transmissioncharacteristics (e.g., signal strength) via feedback from the basestation. Thus, if the transmission characteristics become poor (e.g.,signal strength is nearing or is below a particular strength threshold)for the antenna presently in use for transmission, for example, thesecond antenna 120, then the main controller 160 can test thetransmission characteristics of the other antenna, for example, thefirst antenna 110, by coupling the transmitter module 140 to the firstantenna 110. In evaluating the transmission characteristic of theantennas 110, 120, the main controller 160 may use feedback informationfrom the base station (e.g., closed loop power control). If, in thisexample, the first antenna 110 has the better transmissioncharacteristics, then the main controller 160 maintains the couplingbetween the transmitter module 140 and the first antenna 110. The maincontroller 160 then monitors the transmission characteristics of thefirst antenna 110. On the other hand, if the main controller 160determines that the first antenna 110 does not have the bettertransmission characteristics, then the main controller 160 may controlthe switching module such that the second switch 180 couples thetransmitter module 140 to the second antenna 120.

In another exemplary embodiment, after the main controller 160 has, forexample, switched antennas from the first antenna 110 to the secondantenna 120 to improve, for example, transmission characteristics, themain controller 160 can then attempt to match the receptioncharacteristics with the new transmission characteristics. In thisexample, if the second antenna 120 has a transmission characteristicwhich includes a strength parameter of a particular quantity, then themain controller 160 tests the reception characteristics of the firstantenna 110 and the second antenna 120 to evaluate which one has thereception characteristic, in particular, for this example, the strengthparameter, closest to the particular quantity. The antenna 110, 120selected does not necessarily have, for example, the largest strengthparameter, but only the closest matched strength parameter.

In yet another exemplary embodiment, the main controller 160 maintains alist of base stations in range for at least one of the first antenna 110and the second antenna 120. This list can be compiled when the wirelesscommunications device 100 receives signals from all the base stations inrange of the wireless communications device 100 during, for example, aregistration process or other initial process. Furthermore, the list canbe updated periodically or aperiodically (e.g., triggered by aparticular condition or event). Accordingly, if the transmissioncharacteristics of the antenna presently being used for transmissionbecomes poor, then the main controller 160 can test the transmissioncharacteristics for each of the antennas with each of the base stationson the list. Based upon such tests, a switch in antenna or base stationmay follow. If the reception characteristics of the antenna presentlybeing used for reception becomes poor, then the main controller 160 cantest the reception characteristics for each of the antennas with each ofthe base stations on the list. Based upon such tests, a switch inantenna or base station may follow.

Thus, it is seen that systems and methods for receiving and transmittinginformation in multipath environments are provided. One skilled in theart will appreciate that the present invention can be practiced by otherthan the preferred embodiments which are presented in this descriptionfor purposes of illustration and not of limitation, and the presentinvention is limited only by the claims that follow. It is noted thatequivalents for the particular embodiments discussed in this descriptionmay practice the present invention as well.

1. A portable wireless communications device, comprising: a firstantenna, having a first reception characteristic at a receptionfrequency (f₁), and having a first transmission characteristic at atransmission frequency (f₂) different from the reception frequency (f₁);a second antenna, having a second reception characteristic at areception frequency (f₁), and having a second transmissioncharacteristic at a transmission frequency (f₂) different from thereception frequency (f₁); a switching module coupled to the firstantenna and to the second antenna; a receiver module selectably coupledto the first antenna and to the second antenna via the switching module;and a transmitter module selectably coupled to the first antenna and tothe second antenna via the switching module;
 2. The portable wirelesscommunications device according to claim 1, wherein the switching moduleincludes a first switch and a second switch, wherein the receivingmodule is coupled to the first antenna and to the second antenna via thefirst switch, and wherein the transmitter module is coupled to the firstantenna and to the second antenna via the second switch.
 3. The portablewireless communications device according to claim 1, wherein the firstand second transmission characteristics include effects of a multipathenvironment.
 4. The portable wireless communications device according toclaim 1, wherein the first and second transmission characteristicsinclude at least one of: signal strength, signal clarity and bit errorrate.
 5. The portable wireless communications device according to claim1, wherein the first and second reception characteristics includeeffects of a multipath environment.
 6. The portable wirelesscommunications device according to claim 1, wherein the first and secondreception characteristics include at least one of: signal strength,signal clarity and bit error rate.
 7. The portable wirelesscommunications device according to claim 1, wherein the controller,comprised a mobile station modem (MSM) and is further coupled to thetransmitter module and the receiver module.
 8. The portable wirelesscommunications device according to claim 1, wherein the first antenna isnot disposed in a same direction as the second antenna.
 9. The portablewireless communications device according to claim 1, wherein the firstantenna is disposed approximately orthogonal with respect to the secondantenna.
 10. A method for communications in a portable wirelesscommunications device, comprising the steps of: monitoring a firsttransmission characteristic of a first antenna at a first frequency(f₁); monitoring a second transmission characteristic of a secondantenna at the first frequency (f₁); monitoring a first receptioncharacteristic of the first antenna at a second frequency (f₂) differentfrom the first frequency (f₁); monitoring a second receptioncharacteristic of a second antenna at the second frequency (f₂);evaluating the first and second transmission characteristics; evaluatingthe first and second reception characteristics; selecting andtransmitting on one of the first and second antennas in response toevaluating the first and second transmission characteristics; andselecting and receiving on one of the first and second antenna inresponse to evaluating the first and second reception characteristics.11. The method according to claim 10, wherein the step of monitoring thesecond reception characteristic is initiated only when the firstreception characteristic reaches a particular threshold value.
 12. Themethod according to claim 10, wherein the step of monitoring the secondreception characteristic comprises the step of testing the secondantenna by coupling the receiver module to the second antenna instead ofthe first antenna.
 13. The method according to claim 10, wherein thestep of selecting and receiving is initiated only when the secondreception characteristic is better than the first receptioncharacteristic.
 14. The method according to claim 10, wherein the stepof selecting and transmitting is initiated only when one of the firstand the second transmission characteristics more closely matches one ofthe first and second reception characteristics selected for reception.15. The method according to claim 10, wherein the step of monitoring thesecond transmission characteristic is initiated only when the firsttransmission characteristic reaches a particular threshold value. 16.The method according to claim 10, wherein the step of monitoring thesecond transmission characteristics comprises the step of testing thesecond antenna by coupling the transmitter module to the second antennainstead of the first antenna.
 17. The method according to claim 10,wherein the step of selecting and transmitting is initiated only if thesecond transmission characteristic is better than the first transmissioncharacteristic.
 18. The method according to claim 10, wherein the stepsof monitoring the first and the second transmission characteristicscomprises receiving feedback information from a wireless communicationsnetwork for use in determining the transmission characteristic.
 19. Themethod according to claim 10, further comprising the steps of:generating a list of base stations within range of the wirelesscommunications device for the first antenna and the second antenna ofthe wireless communications device; if the monitored receptioncharacteristic becomes poor, then testing reception characteristicsbetween the first antenna and the base stations on the list and betweenthe second antenna and the base stations on the list; and if the testedreception characteristic of a particular antenna and a particular basestation is better than the monitored reception characteristic, thencoupling the receiver module to the particular antenna and couplingwirelessly the wireless communications device to the particular basestation.
 20. The method according to claim 10, further comprising thesteps of: generating a list of base stations within range of thewireless communications device for the first antenna and the secondantenna of the wireless communications device; if the monitoredtransmission characteristic becomes poor, then testing transmissioncharacteristics between the first antenna and at least one of the basestations on the list and between the second antenna and at least one ofthe base stations on the list; and if the tested receptioncharacteristic of a particular antenna and a particular base station isbetter than the monitored transmission characteristic, then coupling thetransmitter module to the particular antenna and coupling wirelessly thewireless communications device to the particular base station.